Escapement



Nov. 7, 1933.v F. FRANZ 1,934,611

ESCAPEKENT Filed Nov. 29. 1929- Patented Nov. 7, 1933 marten STAT hATENi@QWEQE ESCAPEMENT Application November 29, 1929 Serial No. 419,358

1 Claim.

This invention relates to escapements, and with regard to certain morespecific features, to impulse escapements.

Among the several objects of the invention may be noted the provision ofan escapement for gear trains and the like in which rocking anchorsand/or pallets are eliminated and in which the radius of application ofthe impulse from a controlled train is effected at a greater drivingradius 107 than the braking radius of the escapement, thereby permittingthe use of a stronger and more reliable hair spring and/or a relativelyweaker driving spring in the said train; the provision of a device ofthe class described in which the braking force is reduced and impulseforce increased;'

and the provision of a device of the class described which isexceedingly simple in construction and reliable in operation.

Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly comprises the elements and combination ofelements, features of construction, and arrangements of parts, steps andsequence of steps, which will be exemplified in the structurehereinafter described, and the scope of the application of which will beindicated in the following claim.

In the accompanying drawing in which are illustrated one of variouspossible embodiments 3a of the invention Fig. 1 is a cross section takenon line 11 of Fig. 2, illustrating the invention in elevation; and,

Fig. 2 is an end elevation, certain supporting plates being shown insection.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawing.

Referring now more particularly to Fig. 1 there is illustrated atnumeral 1 a balance staff, supported in suitable bearings 3 (Fig. 2).This staiT 1 carries relatively fixed thereto a balance Wheel 5 and anescapement drum 7. The balance wheel 5 is of suitable diameter andWeight adapted to provide a moment of inertia which will efiect suitableoscillation or vibration of the staif 1 and escapement drum 7 underaction of a vibrating hair spring 9. The hair spring 9 is suitablyatached to the staff 1 and forms a spiral there around, the other end ofsaid spring 9 reacting against a fixed hair spring stud 11 to which saidhair spring is fastened.

Rotatable with an escapement shaft 13 is an escapement wheel 15. As isknown in the art, the escapement shaft 13 is connected in a suitablegear train or other mechanical linkage or train, said train beingadapted to be controlled by the escapement herein described. Thismechanical train is of the type ordinarily driven by a main spring orthe like, the purpose being that the 60 main spring or the like drivesthe train to perform a predetermined function, such as keeping time,operating other mechanisms or the like. The main spring provides theenergy for the train and the escapement permits it to run down only at apredetermined rate, rather than uncontrolledly.

In order to provide my improved escapement, the escapement wheel 15 isprovided with driving teeth 1'7 and the drum '7 is provided with asuitable slot 19 which permits passage, one at a time, of said teeth1'7. However, the teeth 1'7 do not drive the balance wheel assembly bycontacting in said slot 19, but by engagement with an im pulse pin 21engaging near the base of the teeth 17. p

The impulse pin 21, as the drawing shows, is located at a greater radiusfrom the center C of the stair 1, than is the cylindrical surface of thedrum 7 or the slot 19. Hence the escapement wheel 15, under action ofits driving train, has a greater mechanical advantage in driving thebalance stafi assembly by way of the pin 21 than it would have indriving the balance staff assembly by way of the slot 19. Thus, fromthis 5 viewpoint, a heavier -hair spring 9 may be used. inasmuch as thesame force at the pin 21 will overcome a greater resistance than saidforce applied at the slot 19, or to state the inverse proposition, forthe same strength of hair spring, there will be required less drivingforce when the force is applied at the pin 21, than would be required ifit were applied at the slot 19. Thus, for a given size of hair spring, asmaller main spring can be used and/or smaller hair spring. 5

The operation of the device, referring to the surface of the drum 7 as abraking surface 23, is as follows:

Let it be assumed that the escapement wheel 15 under action of itsconnected gear train and main spring rotates clockwise as indicated bythe arrow 25. What occurs is that a tooth, such as the one designated at17--A, engages the impulse pin 21 and drives the balance wheel staff andassociated parts in a counter-clockwise di- 5 rection as indicated bythe arrow 27. The slot 19 is so arranged that as the tooth 1'7A passesto the right, said slot 19 accommodates said passage. This is known asthe escapement action. Es-

cape of one tooth is permitted. 11o

As the tooth 17-A escapes through the slot 19, it continues to drive theimpulse pin 21 until the saidtooth l7--A slips under the pin 21 which isat this time moving upwardly to the right (Fig. 1). It will beappreciated that the balance wheel assembly during this operation ispartially winding the hair spring 9 to provide a reaction.

As soon as the tooth 1'7A slips from under the raised impulse pin 21,the escapement wheel 15 (which is being driven by the main spring andtrain) is quickly driven further in a clockwise direction and thisresults in the next successive tooth 1'7B striking against the brakingsurface 23. It should be remembered that the slot 19 is at this time tothe right and that the braking surface presented to the tooth 1'7-B iscylindrical. The tooth 1'7-A has by this time entirely escaped from theslot 19 and from under the impulse pin 21.

It will be appreciated that the reaction of the hair spring, as soon asthe tooth 17-A has escaped, tends to return the'slot 19 into a positionadapted to receive the next tooth 1"l-B. but, the moment of inertia ofthe balance wheel and the period of the spring are so arranged thatthere is some lag, and this lag is that which permits of the tooth 17'-Bjumping forwardly and contacting with the braking surface 23.

Next, the inertia of the balance wheel 5 having been expended in storingenergy in the hair spring 9 and the lag period being over, the hairspring 9 vibrates back and drives the balance wheel assembly in aclockwise direction, thus returning the slot to its original positionfor admitting the next tooth which, in the present argument, is saidtooth 1713. It will be noted that braking energy is expended by the hairspring 9 on the return stroke. This is because of the friction betweenthe braking tooth 1'7B and the braking surface 23. In order that themech anism may continue to run, this energy must be re-supplied on thenext impulse,stroke by the escapement wheel 15. It is desirable to havethe braking surface 23 at as short radius as is possible, in order toeliminate the possibility of tooth 1'7B applying sumcient energy tostall the hair spring.

It will be seen, that by placing the impulse pin 21 at a greater radiusthan the braking surface 23, that impulse energy is delivered from theescapement wheel 15 to the balance wheel 5 at a better mechanicaladvantage, and that the braking energy used between a tooth surface andthe braking surface 23 is expended with less mechanical advantage (or atan optimum mechanical advantage) on the system with respect to themechanical advantage of the impulse energy. This is what permits the useof either a heavier hair spring or a heavier main spring or both undergiven conditions. In other words, there is provided a device in whichthe driving radius is greatly increased (to a desirable degree) and thebraking radius is held to a minimum (to a desirable degree) It might bethought that, after the tooth 17A has imparted its impulse to the pin 21and escapes, and the tooth 17B is in braked position balance wheel equalto the distance of the pin-21 therefrom. When the wheel 15 has movedthis far, the crest of tooth 17B is less distant from the center of thebalance wheel than the pin 21, thus providing a barrier past which thepin 21 cannot rotate. Obviously, when the main spring is wound, the hairspring 9 is not nearly powerful enough to force the escapement wheelbackwards by the engagement of the pin 21 on the approaching face oftooth 17B. Even should the main spring become unwound, or run down, thehair spring is still not sufilciently powerful to overcome the inertiaof the escapement wheel and the timing train geared thereto. Thus underno conditions could the balance wheel force the escapement wheel intocounterclockwise rotation, and, by reason of the thus immovable barrierof the tooth 17B, warming of the pin 21 is positively prevented underall conditions.

Another advantage of the invention is that it is quite a simpleprocedure of mechanics or design to change the position of the pin 21.Its positioning is quite independent of the radius of the braking system23. Thus these diflerent elements of the escapement design may be variedat will. Heretofore, when merely the slot 19 and braking surface 23 wereused, every time that the impulse force was to be made greater byincreasing the radius of the drum 1, the braking force also becameproportionally larger. With the present invention when the pin 21 ismoved out from the center C, the impulse force is made greater withoutmaking the braking force greater.

It will be understood that the action above set out for the two teeth17-11 and 17-13 continues between successive teeth, the balance wheel 5oscillating back and forth and permitting the ecape through slot 19 oftooth after tooth. Also, tooth after tooth engages the braking surface23, so that the rate of nmning down of the gear train connected with theshaft 13 is accurately controlled. It will be seen that I haveeliminated oscillating elements such as pallets and anchors whichoperate satisfactorily in only a limited number of positions, preferablyupright. The present escapement will operate in any position into whichthe attachment is placed.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results obtained.

As many changes could be made in carrying out the above constructionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

I claim:

An escapement comprising driving escapement teeth, an oscillable balancestaff, a vibrating spring connected with said staff, said staff havingan escapement slot cut therein, said slot permitting escapement of saidteeth successively, but without contacting said teeth, said staff alsohaving a braking surface thereon, said braking surface being positionedto be contacted by said teeth successively, and impulse means comprisinga pin associated with said staff and positioned to receive the entireimpulse of each of said teeth successively, said impulse means beinglocated at a greater radius from the center of oscillation than saidbraking surface, whereby said impulse is at all times delivered to saidstaff at a greater mechanical advantage than is obtained at said brakingsurface. FREDERICK FRANZ.

